JPS63303066A - Titanium nitride sputtering target - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Background of the invention]

The present invention relates to titanium nitride (TiN) sputter targets, and more particularly to TiN sputter targets formed by high temperature isostatic pressing. The invention further relates to a method for forming a TiN film and a TiN film formed by sputtering a TiN target. The integration of multiple components on a single integrated circuit chip requires sophisticated interconnections to minimize signal delay and simultaneously optimize backing density. Aluminum has been widely used for contacts and interconnects in both bipolar and metal oxide semiconductor (MOS) integrated circuits. However, low-temperature interdiffusion of aluminum and silicon during device sintering, passivation, or packaging can result in gain attenuation and increased junction leakage or even shorting of shallow junction devices. The reliability of the device is
Improvements can be made by interposing a barrier layer between the AI and Si to reduce mass transfer in device processing or contact structures off the D-i. TiN films have been proposed as diffusion barriers in very large scale integration (VLSI) metal processing schemes and solar cell top contacts. The TiN diffusion barrier layer avoids undesirable reactions between contact metals such as aluminum and substrate materials such as silicon, thus allowing the use of aluminum where this would otherwise be prohibited. . Reactive sputtering is a well known method for forming TiN films. As is well known to those skilled in the art, sputtering involves the transport of material from a target to a substrate. Ejection of target material is accomplished by bombarding the surface of the target with gas ions accelerated by a high voltage. Atomic-sized particles are ejected from the target as a result of momentum transfer between the incident ions and ions of the target material. The turf particles traverse the vacuum chamber and are substantially deposited onto the substrate in the form of a thin film. N! for microelectronics applications! Since the TiN film is formed as part of the layer structure by reactive sputtering, the AI digit cannot be present with the Ti target in the sputtering chamber. If two targets are placed in the same chamber, an AIN can be formed. Therefore, with reactive sputtering, a TiN7 (lumen) is typically formed on a layer such as TiSi* in a first sputtering chamber with a Ti target, while A
One layer is formed on the TiN film in a second sputtering chamber with an A1 target. in this way,
Reactive sputtering is difficult to perform. Wittmer's literature (Barrier Layers)
:Pr1nciples sat Applicari
oms in Micro-eleclru+ics,
” J, Vsc, Sci, Tscb++o1.
A. (2). 273 (+914)), typical sensitivities for stoichiometric TiN thin films were produced by a reactive sputtering range between about 20 and 70 micron-ohm-cm. Although these low resistivity levels are desired, they are difficult to achieve on an industrial scale. Rapid thermal nitridation (RTN) is another method for forming TiN films. The method is advantageous because the TiN film is formed in place. Typically, Ti is sputtered onto the substrate. The Ti film is then heated to about 1,000° C. and N is introduced to form a TiN film. The disadvantages of rapid thermal nitriding are that the thickness of the TiN film is difficult to control, the TiN film is non-uniform, and harmful gases such as NH, are present. Sputtering of TiN targets, where the targets are formed by hot pressing, is another well known method for forming TiN films. The TiN target is formed by simultaneously applying heat and pressure to the TiN goo at a temperature high enough to sinter the TiN powder to be produced. T formed by this method
The iN target has a density of about 1 s% of the theoretical density of 100% pure TiN. Resistivity for TiN films formed by sputtering of hot press formed TiN targets tends to be about 100 micron-ohm-cm. Sputtering targets and methods are desired where a layered structure having a TiN film is formed in one sputter chamber and the resulting TiN film has a resistivity of about 70 micron-ohm-cm or less.

[Summary of the invention]

It has been found that TiN films with resistivities on the order of 30-70 micron-ohm-cm are easily obtained by sputter deposition using high density TiN targets. These targets are TiN
characterized by a density that is at least about 90% of the theoretical density of . Typically these targets have a nominal purity of at least 99.99%. Targets are typically obtained by high temperature isostatic pressing. It is believed that the low resistivity of the TiN74 lumes produced in accordance with the present invention is at least in part a function of the oxygen concentration of the sputtering target. The sputter target is about 1,000~to, +loOppm (weight), preferably 5,000~? , 000 pp of oxygen is considered desirable. Additionally, the form in which oxygen is present in the sputter target is also believed to be important. Oxygen is known to play an important role in TiN films. Nicolette's literature ("Dirlusioa")
Bsrriers is Th1n Films,'
Th1n 5olid Films 52.415 (
According to the US Pat. No. 6,990,733), some immiscible films do not function as barrier layers because of rapid diffusion along grain boundaries and other structural defects. The repair is
Blocking the diffusion paths with suitable atoms or molecules, i.e., "stuffing" the barrier. When these paths are blocked by suitable impurities, the stuffed barrier conveniently resists heat treatment. For example, when an impurity such as oxygen stuffs a TiN diffusion barrier layer, the oxygen will likely be absorbed along the grain boundaries of the TiN diffusion barrier layer and prevent AI from diffusing into the layer.TiN diffusion The oxygen concentration in the barrier layer can be increased by exposing the TiN diffusion barrier layer to the atmosphere before AI deposition. Furthermore, A I,0 is
It will be formed by annealing, which is known to be very effective against AI diffusion. Although other work is required to corroborate the observations, it appears that the TiN films produced according to the present invention contain a thin coating of titanium oxynitride. However, the oxygen contained inside the nitride is thought to be distributed along the grain boundaries as titanium oxide. At the grain boundaries, the oxide effectively closes the diffusion path and in doing so contributes to the barrier properties of the film without severely compromising the resistivity. The object of the invention is a sputter target for depositing a TiN film consisting of a platform carrying TiN with a density of at least 90% of the theoretical density of 100% pure TiN. Another object of the invention is a method for depositing a TiN film comprising the following steps. providing TiN with a density of at least 90% of the theoretical density of 100% pure TiN;
Sputtering the target under conditions designed to deposit a N film. Another object of the present invention is to provide T
iN films, especially integrated circuits with TiN films as barrier layers. Other objects and advantages of the invention will become apparent from the following description and claims.

[Description of preferred embodiment]

The TiN sputtering target of the present invention has a density of at least 90% of theoretical, typically about 91.
! Characterized by a density of 5%. Although other methods may be used to form the sputter target of the present invention, it is preferably formed by a process known as high temperature equilibration. In a typical method, 1 micron of TiN powder is placed in a steel hot equilibrium press can. The powder is vibrated and compacted, and the can is sealed. The weight is about 10~+00
It is evacuated to micron pressure and placed in a hot isostatic press. Two sets of press conditions have been evaluated and found to be essentially equivalent. In one set, press 1,000 psi at 2 G, 000 psi for 4 hours to generate the target.
Operated with 3SO'O. In another set, the press is operated for 2 hours at 1 s, 000 psi, 1,350°C. After pressing, the cans are removed from the press and the steel cans are removed from the TiN target by a machine. The TiN cake can be cut into disk shapes with a diameter of about 5 cs+, which can be placed on or bonded to a support in preparation for sputtering. The two methods yield gold sputtering targets with a density of 92-95% of the theoretical target. X-ray diffraction shows that the target material matches exactly the simulated stoichiometric TiN pattern. A representative elemental analysis for impurities in a sputter target according to the present invention is shown in Table 1. Table 1 Elements Si At Co Co Cr Cu FcM (M
. PPM ND ND II 5 61352 ND
I3 sputtering involves transporting material from the TiN target to the substrate. Ejection of the TiN target material is performed by bombarding the surface of the TiN target with gas ions accelerated by a high voltage. Typically, ultra-high purity argon is used. Molecular-sized particles are ejected from the TiN target as a result of momentum transfer between the atoms of the TiN tarded material and the incident ions. These particles are sequentially deposited across a vacuum chamber and onto a substrate as a thin film. Typically, TiN targets are water cooled. Magnetron sputtering equipment is particularly useful in the present invention. Effective sputtering equipment is commercially available. Typically, the TiN deposition rate is high, in the range of approximately 40 Angstroms/sec. TiN can be deposited onto the substrate to a desired thickness. Because conductivity is an inherent property, ie, a property that exists regardless of size, the thickness of the film can be varied as desired to meet a particular application. Typically, the thickness of the TiN film is
It is in the range of about 100-300 am. Table 2 includes effective sputtering conditions and properties of the resulting TiN films. The deposition rate is about 38 angstroms/second, and the thickness of the TiN film is about R
It was oam. The temperature of the substrate is in degrees zero, and the bias is a DC voltage. The stoichiometry of Table 2 was determined by Rutherford backscattering spectrometry (RBS), as is well known to those skilled in the art (as in RI
3S is a non-destructive analytical method that provides a detailed profile of the elements that make up thin film devices. As shown,
Ti, N and 01 were present as the main components of the film. No argon gas was detected on the film within the sensitivity of the RBS method. Ti vs. Nw in the film. The child ratio is 0.9-1. according to the RBS results. It changed with lH. It is clear that the stoichiometry is strongly dependent on the sputtering conditions shown in Table 2. 4 table 2
The resistivity, expressed as , is in the range of 38 to 65 micron-ohm-cm. Acceptable resistivity is approximately 30~
In the range of 70 micron-ohm-cm. As shown in Table 2, heating the substrate resulted in a film with a resistivity of 3m-51 micron-ohm-cm. Biasing apparently does not affect the resistivity of the film. The film samples were golden in color and the depth profile compositions in Table 3 below were determined by electron spectroscopy (ESCA) for chemical analysis. As is well known to those skilled in the art, ESCA is a method of electron spectroscopy in which a sample is irradiated with a monochromatic X-ray beam and the resulting energy r of 7 otoelectrons is measured.
1-m. The sputtering rate was 20 angstroms per minute, and the accuracy of the results was ±10%. The binding energies showed that Ti and N exist in the compound cedar form. The film surface of the ESCA outer shape is made of titanium.
It is made of oxynitride, and the inside of the film is made of TiN. Table 3 Sample A 9 51.0g 44.12 C121, sIO
,27415! , 0144. ! SIJ! 11.
77 0.009! 53.2! 43.75 1.
9! 1.07 0.0G sample B! 52.9943.61 174 0.67 0.
0011 S2. H43,7619+ LH0,0
09954,4543,06+,55 0.54 0.
00X-ray diffraction was used to determine the film structure. TiN has a face-centered cubic structure (FCC) comparable to sodium chloride (N*C1k). TiO is isomorphic to TiN. X-ray diffraction showed that the TiN target material matched exactly with the pseudostoichiometric TiN pattern, whereas the evaporated TiN74 lumen (11l
) and (20G) showing a shift in the crystallographic plane spacing of the reflections. Table 4 shows (+) the present invention - sputtering of TiN targets formed by high temperature isostatic pressing, (2) reactive sputtering of Ti targets, and (T of DNt).
Rapid thermal nitriding (RTN) of i/S i (100)
A comparison of the properties of TiN films formed by the following methods is shown. Table 4 ['0-60 min] As also shown in Table 4, the TiN film formed according to the present invention has the lowest resistivity, i.e., +0 micron-ohm-C, and the highest deposition rate, i.e., 40 angstroms. It produced 100 m/s. Each TiN74 lume has a lick A I/
T iN/ T isia/ S i (100)
The structure is formed by a diffusion barrier. The diffusion barrier temperature is the highest temperature at which the layer structure was thermally stable for 60 minutes. Using the AI/TiN/Ti5iz/Si (100) layer structure, AI reacts with TiN to form AIN and A
1. Form T i. Consequently, internal diffusion of A1 and Si can lead to grain attenuation and increased junction leakage or even shorting of shallow junction devices. The TiN film formed according to the present invention produced the highest diffusion barrier temperature at 60 minutes, namely 560°C. , Based on the above description, the TiN film of the present invention is:
A I, / TiN/S i and AI/TiN/T
Layer structures such as iSi, /Si are particularly useful in integrated circuits as diffusion barrier layers. TiN films can also be used for local interconnections, contacts between metal and silicide, Ti-Pt
It is being investigated for use as a sticking layer for reaction blocking, high stability solar cells, and CVD tungsten. TiN films can also be used as etch stop layers for reactive ion etching. Although the invention has been described in detail with reference to preferred embodiments, it will be obvious that modifications and changes can be made without departing from the scope of the invention as defined by the claims. Patent Applicant: Parian Associates, Inc.

Claims (1)

Claims: 1. A sputter target for the deposition of titanium nitride films having a target surface consisting of titanium nitride having a density of at least 90% of the theoretical density of 100% pure titanium nitride. 2. The titanium nitride has a molecular weight of about 1,000 to 10,
2. The target of claim 1, comprising 0.000 ppm by weight of oxygen. 3. The titanium nitride is about 5,000 to 7,000 ppm
3. The target of claim 2, comprising a weight of oxygen. 4. The target of claim 1, wherein said titanium nitride has a density of about 92-95% of the theoretical density of 100% pure titanium nitride. 5. The target of claim 1, wherein the target is prepared by subjecting titanium nitride powder to high temperature equilibrium pressure. 6. The titanium nitride powder is heated to a high temperature equilibrium pressure of about 1,350°C and heated to about 20,000 psi (1,406 kgw) for about 4 hours.
6. The target 7 of claim 5, wherein the titanium nitride powder is exposed to a high temperature equilibrium pressure of about 1,350° C. and about 15,000 psi (1054.5 kg) for about 2 hours.
6. The target according to claim 5, wherein the target is exposed to w/cm^2). 8. A titanium nitride film having a resistivity of about 30 to 70 micron-ohm-cm, the titanium nitride film yielding a titanium nitride target having a density of at least 90% of the theoretical density of 100% pure titanium nitride. and a film prepared by sputtering the titanium nitride target to deposit a titanium nitride film. 9. The film of claim 8, wherein the oxygen is present in the form of titanium oxynitride on the surface of the film and as titanium oxide inside the film, and the titanium oxide is arranged along grain boundaries. . 10. The film of claim 8, wherein the titanium nitride film is used as a diffusion barrier layer in an integrated circuit. 11. The film of claim 8, wherein the titanium nitride film is used as an etch stop layer. 12. A method for depositing a titanium nitride film on a substrate, the method comprising: at least 90% of the theoretical density of 100% pure titanium nitride;
%; and sputtering the target under conditions designed to deposit a titanium nitride film onto the substrate. 13. The method of claim 1, wherein providing the target includes subjecting titanium nitride powder to high temperature isostatic pressing.